OMAP4: EMIF: code cleanup and clarification

Removed unused fields of emif_regs structure and
functions that initialize or change them.

Also changed few names of emif_regs members
to match register names.

This made the code easier to understand and read
as well as made it a little bit faster

Change-Id: I0485a01b7f03e922b5a2e69bfb03c2ed941fcf3b
Signed-off-by: Ruslan Bilovol <ruslan.bilovol@ti.com>

Conflicts:
	arch/arm/mach-omap2/emif.c